Britain's government expanded a programme of daily Covid-19 tests on Monday to reduce staff absences caused by a high number of new cases and strict rules on isolation for their close contacts.
Hundreds of thousands of British workers who were in close contact with those infected have been required to isolate themselves for 10 days, creating staff shortages in critical areas.
This rule is due to end for fully vaccinated workers on August 16, and before then workers may be exempt if their employer is chosen to host government-run daily Covid-19 tests.
Isolation is normally required even if someone later has a negative test for Covid-19.
Last week the programme was announced for 800 workplaces in the food industry, transport sector and some police, firefighters and border guards.
On Monday Britain's Health Ministry said it would set up daily testing at another 1,200 workplaces including military bases, prisons and pharmaceuticals factories, as well as for rubbish collectors, essential utilities and tax collectors.
"Whether it's prison guards reporting for duty, waste collectors keeping our streets clean or workers in our energy sector keeping the lights on, critical workers have been there for us at every stage of this global pandemic," Health Minister Sajid Javid said.
But the new daily testing programme will be unavailable to by far most private-sector employers.
Growth in the first half of July slowed sharply because of widespread worker absence and supermarkets have warned of difficulties in fully restocking shelves.
Britain has suffered Europe's second-highest death toll from Covid-19, after Russia, and in recent weeks cases have increased because of the more infectious Delta variant.
But deaths have been much lower in this wave of infections, after widespread vaccination.
The latest data suggests Britain may have passed the peak of infections in this wave, despite a relaxation in Covid-19 rules in England on July 19.
But more than 250,000 people still tested positive in the past week.